Math help

[Oreo]

Ok, which one of those is meant to be a + symbol...?

the first = is a +

edit;
sorry didnt notice u replied tim, let me read
And thanks Peter

Thanks guys, i kind of understand now. I'll get my math teacher to run me through it tommorow

 

[Apokalipse]

Revising math, i have come across 2 things i can not do. Do not laugh, my Math is terrible.

The question in the revision book is "Factorise 2x^2 -7x -15". Now i can factorise, but this has thrown me

2x² -7x -15
= 2x² - 10x + 3x - 15
= 2x(x - 5) + 3(x - 5)
= (2x + 3) (x - 5)

also, How do i find the line of symmetry on any given graph, in particular the graph of 2x^2 -7x -15.

The line of symmetry with a quadratic equation is at the turning point. So find it by putting the equation in turning point form, by using the completing the square method:

2x² - 7x - 15
= x² - (7/2)x - 15/2
halve and square the factor in front of x (not x²), then add and subtract that number to the equation. You now have a factor for a perfect square.
= [x² - (7/2)x + (7/4)²] - (7/4)² - 15/2
= [x² - (7/4)x -(7/4)x + (7/4)²] - 49/16 - 120/16
= (x - 7/4)² - 169/16

the turning point is x = -7/4 and y = - 169/16

To complete the rest of the factorisation using the completing the square method, do this:
(x - 7/4)² ± √(169/16)²
= (x - 7/4)² ± (13/4)²
= (x - 7/4 + 13/4) (x - 7/4 - 13/4)
= (x + 6/4) (x - 20/4)
= (x + 1.5) (x - 5)

Also the question of, "Solve the simultaneous Equations"

y= x + 7
x^2 + Y^2 = 25

x² + (x + 7)² = 25 (since y = x + 7)

 

[Tim]

Hey Apokalipse, how'd you do those power signs?

 

[Oreo]

2x² -7x -15
= 2x² - 10x + 3x - 15
= 2x(x - 5) + 3(x - 5)
= (2x + 3) (x - 5)

The line of symmetry with a quadratic equation is at the turning point. So find it by putting the equation in turning point form, by using the completing the square method:

2x² - 7x - 15
= x² - (7/2)x - 15/2
halve and square the factor in front of x (not x²), then add and subtract that number to the equation. You now have a factor for a perfect square.
= [x² - (7/2)x + (7/4)²] - (7/4)² - 15/2
= [x² - (7/4)x -(7/4)x + (7/4)²] - 49/16 - 120/16
= (x - 7/4)² - 169/16

the turning point is x = -7/4 and y = - 169/16

To complete the rest of the factorisation using the completing the square method, do this:
(x - 7/4)² ± √(169/16)²
= (x - 7/4)² ± (13/4)²
= (x - 7/4 + 13/4) (x - 7/4 - 13/4)
= (x + 6/4) (x - 20/4)
= (x + 1.5) (x - 5)

x² + (x + 7)² = 25 (since y = x + 7)

Thanks man!

Just did my GCSE Math exam. Reckon i got about 40 to 50 out of 70, so meh. Not to dissapointed, could of done quite a bit better, however.

 

[patonb]

Wow sooooooooooo many memmories are flooding back............. make them stop!

 

[Oreo]

Wow sooooooooooo many memmories are flooding back............. make them stop!

They're not memories i'd want to remember, i assure you